Stanford Engineers Develop Roadside Marijuana Test

As more states legalize the use of marijuana,Stanford University engineers hope to solve one reoccurring concern: how police can keep high drivers off the road.

A team led by Stanford professor Shan Wang created a portable device able to detect THC molecules in saliva. Drivers involved in crashes with elevated levels of THC in their blood are three to seven times more likely to be responsible for the incident than drivers not under the influence, the National Institute on Drug Abuse reports. Studies show those who smoke at least an entire joint can be impaired.

Officers who suspect marijuana intoxication could use a cotton swab to wipe the inside of a driver’s mouth, test it in the new device (called a potalyzer) and get results viewable on a smartphone or laptop in just a three minutes, according to a Stanford news release. Currently, officials rely on blood, breath or urine tests that aren’t always accurate. Saliva tests exist, but also aren’t completely accurate.

Tom Abate, associate director of communications at Stanford Engineering, said he does not know how this test compares to others on the market, but Stanford’s device does measure the presence of THC and concentration.

Stanford’s device can show THC in the range of 0 to 50 nanograms per milliliter of saliva, within most measurements of impairment, the release states. Colorado law says drivers with five nanograms of active THC in their blood can be prosecuted.